Ceramic pressure measurement cells of the field of the invention comprise a ceramic platform and a ceramic measuring membrane, wherein the platform and the measuring membrane are joined with one another along a peripheral seam such that a measuring chamber is formed between the platform and the measuring membrane, wherein the joint comprises an active hard solder, or braze. An established ceramic material for measuring membranes and the platform is corundum, wherein as active hard solder, or braze, especially a Zr63Ni22Ti15 active hard solder, or braze, is used.
For joining the components, they are arranged in the desired position relative to one another in a high vacuum oven and heated, until the active hard solder, or braze, melts at 900° C. and actively forms a bond with the ceramic. Following the melting, the pressure measuring cell is allowed to cool in the furnace under vacuum and, in given cases, at times, with the addition of a protective gas.
From calorimetric measurements performed on the solder, it is known that the liquidus temperature lies at about 860° C. and the solidus temperature at about 800° C. The crystallizing of phases from the melt takes place in this temperature range. Other phase formations are possible below the solidus temperature. It is known that always the same thermodynamic phases form.
Investigations with reflection electron microscopy (REM) on sections through joints have led to determining that different segregated phases take up large regions within the joint. Since this involves phases with a different composition, it is to be assumed that they differ in properties, such as the thermal coefficients of expansion, and compressive, respectively tensile, strengths. As a result, the quality of the joint can be degraded as regards strength, sealing, and/or manufacturing yield.